Step 1: Process Comprehension.
Sedimentation involves separating particles from a fluid by gravity-induced settling. This technique is prevalent in sectors such as water purification and mineral extraction.
Step 2: Option Clarification.
- (D) Sedimentation accurately describes the separation of particles based on their dimensions, form, and density. - (A) Classification is the sorting of particles by size. - (B) Froth flotation is employed for separating non-polar particles. - (C) Thickening serves to augment the solid concentration within a slurry.
Final Determination: \[\boxed{\text{D) sedimentation}}\]